Variable volume pump with protection against overheating



Sept. 13, 1965 E. N. CONNOY ETAL 3,272,133

VARIABLE VOLUME PUMP WITH PROTECTION AGAINST OVERHEATING Filed Feb. 17,1964 5 Sheets-Sheet 1 M MW .Iz/ym AZ Jammy 71 1mm W/Yaflmazm JamiWFarZrzzz [arias/5f Wbzlmz'! Sept. 13, 1966 E. N. CONNOY ETAL 3,272,138

VARIABLE VOLUME PUMP WITH PROTECTION AGAINST OVERHEATING Filed Feb. 17,1964 5 Sheets-Sheet 2 INLET 32 30 OUTLET\9 I9 27 z/ 35 32 fiwm Jayme AZJammy Fla/2am W 1Y0 p 1956 E. N. CONNOY ETAL 3,272,138

VARIABLE VOLUME PUMP WITH PROTECTION AGAINST OVERHEATING Filed Feb. 17,1964 5 Sheets-Sheet 5 United States Patent 3,272,138 VARIABLE VOLUMEPUMP WITH PROTECTION AGAINST OVERHEATING Eugene N. Connoy and Richard W.Hoffmann, Minneapolis, Iames W. Parkin, Burnsville, and Charles H.Whitmore, Savage, Minn, assignors to Continental Machines, Hue, Savage,Minn, a corporation of Minnesota Filed Feb. 17, 1964, Serial No. 345,2381 Claim. (Cl. 103120) This invention relates to pumps, and refers moreparticularly to variable volume pumps, wherein the volume of fluiddelivered by the pump varies automatically in accordance with therequirements of a fluid pressure responsive system supplied by the pump.

While the invention is applicable to variable volume pumps regardless oftype, it is especially well adapted to rotary vane-type pumps wherein arotor having vanes slidably projecting from its periphery rotates abouta fixed axis within a ring that encircles the rotor and shifts towardsand from concentrici-ty with the rotor as the volume of fluid deliveredby the pump varies. At maximum flow, the ring is farthest fromconcentricity and at no flow the ring is very nearly concentric with therotor. It never reaches absolute concentricity since a slight amount offluid always escapes from the pressure zone of the pump despite the factthat fluid does not enter the system through the outlet of the pump.This slight flow is called case drain, and in most vane-type pumps, asit is in the pump shown herein to illustrate one embodiment of thisinvention, this case drain is used to lubricate the bearings of thepump.

One of the problems encountered in variable volume pumps concerns thedissipation of the heat resulting from the operation of the pump. Aslong as the system supplied by the pump requires the flow of fluid,there is usually an adequate heat dissipating circulation through thepump, but when the pump is operating at or near no flow conditions andpractically all of the driving energy fed into the pump is convertedinto heat, the danger of overheating and consequent seizing of the pumpis very real, particularly in pumps having a high rated capacity.

In pumps which do not have a very high rated capacity, radiation fromthe external surfaces of the pump body plus the relatively small flow offluid from the pressure zone as case drain is usually adequate toprevent dangerous overheating. Thus, for instance, rotary vanetype pumpsoperating at 1800 rpm. and having a nominal output volume of six gallonsper minute, exhibited no serious overheating even at extended period ofno flow operation.

However, it was found that when the rotor speed of these pumps wasincreased from 1800 to 3600 r.p.m. with a view toward stepping up theoutput of the pump from a nominal six gallons per minute to a nominaltwelve gallons per minute, the overheating problem became extremelyacute. Since the size of the pump, that is, its physical dimensions, wasnot increased in doubling its speed of operation, there was no moreradiating surface available than before. The only hope of preventingoverheating thus resided in increasing case drain. To increase casedrain in a rotary vane pump more clearance is required between the endfaces of the rotor and the port and wear or thrust plates between whichthe rotor is confined; but when this is done the resulting abnormallyhigh case drain makes the pump very inefficient.

The dilemma which this discovery posed motivates the present invention.As will be recognized, therefore, it is the purpose and object of thisinvention to not only provide some means of effecting sufficientcirculation of fluid from the high pressure zone of a variable volumepump at times when the pump is operating under no flow conditions, butto do this without sacrificing any of the efliciency of the pump.

Stated in another way, it is the object of this invention to provide avariable volume pump wherein heat dissipating flow of fluid from thepressure zone of the pump adequate to preclude overheating is maintainedwhenever the pump is operating at or near no flow conditions, butwherein the means for effecting such heat dissipating circulation isrendered inoperative whenever the volume of fluid flowing from the pumpoutlet is sufficient to satisfactorily dissipate the heat that isgenerated in the pump.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claim, it beingunderstood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaim.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention, constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

FIGURE 1 is an end View of a rotary vane-type variable volume pumpembodying this invention, parts of said view being broken away and insection;

FIGURE 2 is a sectional view of the pump taken on a plane parallel withthe rotor axis and designated by the line 2-2 in FIGURE 1;

FIGURE 3 is a view from the end of the pump opposite that shown inFIGURE 1, and also having parts broken away and in section;

FIGURE 4 is a sectional view through FIGURE 1 on the plane of the line44;

FIGURE 5 is an exploded perspective view of the rotor and certainadjacent parts of the pump;

FIGURES 6 and 7 are fragmentary detail views of a portion of the rotor,its encircling ring and the confining port and thrust plates,illustrating by comparison between these two views an essential featureof this invention; and

FIGURES 8 and 9 are respectively detail sectional views through FIGURES6 and 7 on the planes of the lines 88 and 9-9.

Referring now particularly to the accompanying drawings in which likenumerals indicate like parts throughout the several views, the numeral 5designates the body of the pump which comprises a main section 6 andacover 7 bolted thereto. The inlet 8 and the outlet 9 of the pump are inthe main section 6 and open downwardly through the mounting base 10 ofthe pump. The body of the pump defines a hollow chamber 11 in which therotor 12 of the pump is located, the rotor being fixed to its shaft 13which is journaled in bearings 14 and 15 located respectively in themain section 6 and the cover 7. The end of the shaft which is journaledin the main section protrudes therefrom to provide for connection of thepump rotor with the shaft of a drive motor, not shown.

The rotor 12 has a plurality of substantially radially disposed slots 16extending in from its periphery and opening to the opposite ends offaces of the rotor which are fiat. Slidably received in these slots arevanes 17, the outer end portions of which project beyond the peripheryof the rotor to span the space between the rotor and the inside surface18 of a pressure ring 19 which encircles the rotor. Thus the ring 19,the rotor, the vanes and end walls provided by a port disc or plate 20and a thrust plate or disc 21 between which the assembled rotor, vanesand pressure ring are confined, coact to define fluid pumping chambers22 which travel in circular orbits as the rotor revolves.

A governor spring 23 which reacts between an adjustable spring seat 24in the pump body and the adjacent side of the pressure ring 19,yieldingly urges the ring towards its position of maximum eccentricitywhich, in the pump illustrated, is defined by a fixed abutment or pad 25on the pump body. The force with which the spring 23 acts upon thepressure ring determines the pressure which the pump will develop andmaintain.

Because of the eccentricity between the pressure ring 19 and the rotor,the pumping chambers 22 increase in size during one-half of theirorbital rotation about the rotor axis and decrease in size during theother 180 of rotation. As the pumping chambers 22 increase in size orvolume, they sweep past and communicate with arcuate inlet ports 26 and27 located respectively in the port plate 20 and in the thrust or wearplate 21, to receive fluid therefrom; and, as they decrease in size,they sweep past and communicate with an arcuate discharge port 28 whichcommunicates wit-h the pump outlet 9.

In this manner fluid is drawn into the pump through its inlet 8 which,in practice, is connected with the reservoir of the system, not shown,or any other suitable source of fluid, and forced from the pump throughits outlet which, of course, is connected with the system to besupplied. It follows, therefore, that both a suction zone to which theinlet leads and a pressure zone at all times communicated with theoutlet of the pump, exists inside the pressure ring 19.

As the flow requirements of the system decrease, the fluid pressureinside the pressure ring causes the ring to shift towards concentricitywith the rotor in opposition to the governor spring 23, and, in sodoing, correspondingly reduces the volume of fluid delivered by thepump. This fluid pressure inside the pressure ring also applies a forceon the ring tending to displace it from its desired path of translatorymotion towards and from concentricity with the rotor, the direction ofthis force being upward, as viewed in FIGURE 1, so that the ring is heldagainst an abutment 29 fixed in the pump body. Since the surface on theabutment 29 against which the pressure ring bears is fixed, the ringrolls thereon as it shifts back and forth in consequence of the varyingflow demands of the system.

The rolling of the ring on the abutment 29 in conjunction with the otherforces acting upon the pressure ring, causes the ring to creep aroundthe rotor and thereby uniformly distribute the wear on the inner surfaceof the ring which results from the sliding or rubbing engagement of thevanes therewith. This wear distributing feature, however, is no part ofthe present invention, being instead the subject matter of the copendingapplication Serial No. 337,043, filed January 10, 1964, by Charles H.Whitmore, Russell G. Winquist and Sheldon E. Thorson. As more fullydescribed in that application, the inner ends of the slots 16 in therotor are successively communicated with the suction and pressure zonesof the pump so that fluid pressure acts on the inner ends of the vanesto press them outwardly into firm engagement with the inside surface ofthe pressure ring. However, and in spite of the fact that the vanes arethus pressed against the inside surface of the pressure ring, some fluidwill flow past the vanes from one pumping chamber 22 to the next. Thisis called slippage, and obviously it has an adverse effect upon theefliciency of the pump.

The flow of fluid from the pressure zone through the running clearancewhich must be provided between the opposite end faces of the rotor andthe port and thrust plates 20 and 21, and which leaves the pump as casedrain, also adversely effects the eificiency of the pump, but this flowcan be, and in the present pump is, used to lubricate the bearings.Thus, as best seen in FIGURE 4, the fluid which escapes from thepressure zone through the clearance between the port plate or disc 20and the adjacent side of the rotor, flows through the bearing 14 andthen 1. 2138 1 pump through a case drain port 30,

which, like the inlet and outlet, opens downwardly through the base 10of the pump. By the same token, the fluid which escapes from thepressure zone through the running clearance between the thrust plate ordisc 21 and the adjacent side of the rotor, flows through the bearing 15and, from there, is conducted through passage means 31 to the hollowinterior of the pump body to be exhausted therefrom through a passage 32which leads to the case drain port 30.

The running clearance provided between the opposite faces of the rotorand the port and thrust plates between which the rotor is confined, andhence the amount of fluid which leaves the pressure zone of the pump ascase drain, is governed by the thickness of a shim or shims 33interposed between the thrust or wear plate 21 and the adjacent innerface of the cover 7. Obviously, the thinner the shim or shims, thegreater will be the clearance and, consequently, the larger the casedrain flow-all other contributing factors being the same. Equallyobvious is the fact that if the case drain flow is too large, theefficiency of the group suffers, since fluid which is permitted to leavethe pressure zone of the pump as case drain performs no useful work,other than the lubrication of the bearings. Accordingly, the shimthickness should be chosen to provide only the necessary runningclearance.

As explained hereinbefore, as long as the system requires fluid flow,the heat which is produced during operation of the pump is adequatelydissipated or carried off by the fluid circulating through the pump.Case drain flow, of course, also carries off some of the heat and, inaddition, part of it is radiated from the external surfaces of the pump,but as long as the system demands any appreciable flow it is the fluiddelivered to the system by the pump which carries off the heat. Theproblem arises when there is no such flow so that case drain andradiation must be depended upon to prevent overheating.

It is known that a rotary vane type pump operating at 1800 rpm. andhaving a nominal rated capacity of six gallons per minute, hassuflicient case drain and sufficient radiation to preclude overheating,even during extended periods of no-flow operation when practically allof the driving energy imparted to the pump is converted into heat. Butwhen it was discovered that this same pump could be driven at twice thespeednamely, 3600 r.p.m., to achieve a nominal volume rating of twelvegallons per minute, provided that cavitation could be avoided, thenormal case drain and radiation was unable to dissipate enough heat toprevent serious overheating and very real danger of having the pumpseize.

Although it does not constitute any part of the present invention, itshould be explained that cavitationwhich was observed when the pump, inexactly the same condition as it had been for 1800 rpm. operation, wassimply driven at a higher speedwas overcome by simultaneously bringingthe fluid into the pumping chambers from both sides of the rotor. Asshown in FIGURE 2, this is accomplished by a crossover passage 34leading from the inlet 8 through the main section of the body and intothe cover 7 which has a cored transfer passage 35, the mouth 36 of whichis arcuate and registers with the arcuate inlet passage 27 in the wearplate 21.

The solution of the overheating problem which this invention provides,consists in providing controlled communication between the space insidethe pressure ring and an exhaust passage which comprises the hollowinterior of the pump body, the passage 32 and the case drain port 30.This is accomplished by the simple expedient of providing a shallownotch or recess 37 in the inner face of the port plate or disc 20 and ofthe thrust or wear plate or disc 21. In effect, these notches orrecesses may be considered ports or months through which the exhaustpassage connects with the pressure zone of the pump. The notches orrecesses are so located and are of such size and shape that the adjacentflat end faces of the pressure ring extend across them to close thesemouths by closing off communication between the notches or recesses andthe space inside the pressure ring when the ring is in any position itoccupies during any appreciable flow of the pump; but not when the ringis in its position most nearly concentric with the rotor, which positionit occupies when no fluid flows from the pump to the system. The properlocation for the notches or recesses 37 is thus :on the plane oftranslatory motion of the pressure ring as it shifts towards and fromconcentricity with the rotor.

The length of the notches or recesses in the direction of pressure ringadjustment must be so related to the thickness of the ring wall, or-moreaccurately-the radial width of its flat end faces, that the inner end 38of the notches or recesses opens to the inside of the ring only whenthere is no flow or practically no flow from the pump outlet. The outerends of the notches or recesses are at all times open to the hollowinterior of the pump body. This relationship between the size of thenotches or recesses and the pressure ring is best illustrated in FIGURES6 to 9, inclusive.

The notches or recesses 37 and the adjacent flat end faces of thepressure ring thus coact to form valves governing communication betweenthe pressure zone of the pump and the exhaust passage leading from thepump. When these valves are open, the mouths of the exhaust passage areopen and fluid flows from the pressure zone of the pump and out of theexhaust passage. The rate at which it flows is greater than normal casedrain, as it should be; but obviously, even then, the flow must berestricted or limited. The dimension of the notches or recesses toprovide the proper rate of how may be readily calculated. For purposesof illustration, a pump driven at 3600 rpm. and operating at no flow and1000 psi, must have a circulation of at least 1500 millil-ters perminute (.39 g.p.m.) out of its pressure zone to prevent seizing due tooverheating, but only 300 to 400 milliliters per minute when the pump isdelivering one or more gallons per minute.

Preferably, the inner ends 38 of the notches or recesses are convexlycurved, as shown, rather than square, to efliect a progressivelyaccelerated cessation of heat dissipating flow from the pressure zone,rather than abrupt termination thereof, as the pump begins to deliverfluid to the system.

Although there are two notches or grooves 37 in the embodiment of theinvention shown and described, one at each face of the rotor, it isobvious that only one such notch or groove could be used provided it hadthe required flow capacity.

From the foregoing description, taken in connection with theaccompanying drawings, it will be readily apparent to those skilled inthis art that this invention provides a simple and practical solution tothe overheating problem in variable volume pumps, since it provides foradequate heat dissipating flow or circulation of fluid from the pressurezone of the pump when the pump is operating at or near no flowconditions, while maintaining pressure, but terminates that flow as soonas appreciable flow from the pump to the system supplied thereby begins.

What is claimed as our invention is:

In a variable volume pump of the rotary vane type having (1) a body withan inlet and outlet, and defining a rotor chamber communicating with theinlet and outlet and having opposite side walls,

6 (2) bearing means in the body, ('3) a rotor journalled in said bearingmeans and confined in the chamber between the side walls thereof, therotor having vanes slideably projecting from its periphery, and (4) aring which encircles the rotor and is shiftable towards and fromconcentricity with the rotor and coacts with the vanes to providepumping chambers by which fluid is taken from the inlet, pressurized anddelivered to the outlet at a substantially constant pressure but in avolume which varies with the position of the ring, the volume beingmaximum when the ring is farthest from concentricity and zero when thering is concentric with the rotor,

so that part of the space inside the ring is at all times communicatedwith the outlet and during operation of the pump constitutes a pressurezone,

wherein some of the fluid which inevitably leaks from said pressure zoneflows to the bearing means to lubricate the same, and wherein the bodyalso has a drain port at all times in communication with the bearingmeans and with the outer portion of the rotor chamber that encircles thering, to receive and carry off fluid which flows through the bearingmeans and fluid which leaks out of the pressure zone into the outerportion of the rotor chamber, the improvement which prevents overheatingof the pumpdue to conversion into heat of the energy expended to drivethe rotor and maintain the pressure when the volume of fluid deliveredby the pump is zero or near zero, and which improvement comprises:

means defining a fluid passage of limited capacity to communicate thepressure zone inside the ring with the outer portion of the rotorchamber and hence with the drain port,

said fluid passage having open communication with the outer portion ofthe rotor chamber and having its mouth in one of the side walls of therotor chamber in position to be covered and closed by the adjacentsurface of the ring whenever the ring is in any position it occupieswhen the volume of fluid delivered by the pump through its outlet issufficient to prevent overheating of the pump and to be uncovered andopen when the ring is in the position it occupies when the volume offluid delivered by the pump is at or near zero.

References Cited by the Examiner UNITED STATES PATENTS 2,637,275 5/ 1953McFarland 103-120 2,649,739 8/ 1953 Huiferd et a1. 103-120 2,651,994 9/1953 DeLancey et al 103-120 2,740,256 4/1956 OMalley 103-120 2,768,58510/1956 Hardy 103-120 2,805,628 9/ 1957 Herndon et a1. 103-120 2,875,6993/1959 Herndon 10 3-1 20 3,120,814 2/1964 Mueller 103-120 MARK NEWMAN,Primary Examiner.

WILBUR J. GOODLIN, Assistant Examiner.

